我为我的firebasecollection-payments设置了以下规则"payments":{"$paymentId":{"totalAmount":{},"balanceAmount":{".validate":"newData.val()和下面编写的云函数来处理该集合的某些更新:exports.calculateBalance=functions.database.ref('payments/{pushId}').onUpdate(event=>{constpaymentRef=event.data.adminRef;constpayment=event.data.val()